1. Field of the Invention
This invention pertains to the field of clutch engaging/disengaging mechanisms. More particularly, it is a device for automatically engaging or disengaging the clutch based upon engine speed.
2. Description of the Related Art
Most motorcycles incorporate a manual transmission coupled to the engine via a multi-plate clutch assembly. Typically, the multi-plate clutch is engaged/disengaged by the driver via a lever mounted on the handlebar. Although the lever operated clutch allows the driver to control the clutch engagement/disengagement, often, motorcycle drivers find the clutch lever difficult to operate smoothly. New riders have difficulty adjusting to smoothly engaging the clutch while operating the throttle to move the vehicle from a standing start. Additionally, experienced riders may need to partially disengage the clutch when traveling slowly to allow the engine to continue running without stalling. Motorcycle racers often have a difficult time controlling the engagement of the clutch and the application of the throttle to maximize acceleration. In another scenario, Off-road motorcycle racers often need to stop the rear wheel suddenly with the rear brake, causing the engine to stall if the clutch is not first disengaged. An automatic clutch can help overcome many of the problems associated with a manual clutch.
Automatic clutches for motorcycles have existed for more than 10 years, primarily for entry-level motorcycles with low power. More recently, retrofit automatic clutches for high-performance motorcycles have become available. Automatic clutches for high-performance motorcycles have many advantages over manual clutches. Currently available retrofit automatic clutches have several disadvantages. They require replacement of or changes to existing clutch parts. Most motorcycle clutch's pressure plates are spring loaded and attached to the clutch inner hub. However, a centrifugal clutch's pressure plate must spin with the clutch's outer basket which is coupled rotationally to the engine to provide engagement force. Existing retrofit automatic clutches require a modified clutch outer basket to bolt the new centrifugal pressure plate to.
Clutch lever override is not possible at high engine speeds. Existing retrofit automatic clutches use a rigid centrifugal engagement mechanism. To disengage the clutch, the entire force of the centrifugal engagement mechanism must be overcome. At higher engine speeds, the increased centrifugal force of the engagement mechanism becomes difficult or impossible to overcome.
The stock pressure plate provides a fixed amount of pressure to the clutch disks. The stock pressure plate force is limited to ensure the clutch can slip if excessive force is sent through the driveline. Existing retrofit automatic clutches transfer all of the force generated by centrifugal engagement mechanism into the clutch disks. At higher engine speeds, the excess centrifugal force can prevent the clutch from slipping in the event an excessive force is sent through the driveline. The excessive force traveling through the clutch may cause a failure in the engine or transmission.
Existing automatic clutches also do not accommodate the specific needs of high torque motorcycles such as high displacement four stroke motorcycles. Engagement of automatic clutches on motorcycles needs to occur at low speeds without sudden and jerky engagement. Accordingly, a better manner of modulation of engagement of automatic clutches is needed.
Additionally, a need exists for an apparatus that automatically engages and disengages the clutch of a vehicle based upon engine speed while also providing a manual override to disengage the clutch via a driver operated handlebar lever. The driver operated handlebar lever should be able to disengage the clutch at any engine speed without excessive force at high engine speed. Furthermore, the apparatus should limit the total amount of force the centrifugal pressure plate applies to the clutch disks.